python

The clean() method validates model instances before saving. I raise ValidationError for invalid data. This runs on form submission and can be called explicitly with full_clean(). I validate cross-field constraints that can't be expressed as field vali

JSONField stores structured data without creating separate tables. I use it for settings, metadata, or varying attributes. Django provides database-level JSON operations via lookups like __contains, __has_key. For PostgreSQL, I get native JSON operato

Bulk operations reduce database round-trips dramatically. I use bulk_create() for inserting many objects at once, bulk_update() for updates, and update() for queryset-level updates. These bypass save() methods and signals for speed. For large datasets

Nested serializers display related data clearly but are read-only by default. To make them writable, I override create() and update() methods. For simple nesting, PrimaryKeyRelatedField or SlugRelatedField works well. For deeper nesting, I validate ne

I treat pandas as the default workbench for structured data. The goal is to make loading explicit, indexes predictable, and selection operations readable under maintenance pressure. I prefer stable column naming, typed parsing for dates, and avoiding

Proxy models create different Python behavior for the same database table. I set proxy = True in Meta. This adds methods or changes default ordering without new tables. Proxy models share the same table as the original. Use cases include different man

Migrations track database schema changes. I use makemigrations after model changes and review generated migrations. For data migrations, I create empty migrations with makemigrations --empty and write RunPython operations. I test migrations on dev dat

Database routers enable read-write splitting for scaling. I direct reads to replicas and writes to primary. The router examines hints and model to make routing decisions. For read-heavy apps, this distributes load across multiple databases. I use usin

The only() method loads specified fields only, while defer() excludes specified fields. This reduces data transfer and memory usage. I use only() when I need just a few fields from large models. For read-only displays, this prevents loading unnecessar

Connection pooling reuses database connections instead of creating new ones per request. I use django-db-pool or configure persistent connections with CONN_MAX_AGE. This reduces connection overhead significantly. For high-traffic sites, I set appropri

Django Debug Toolbar reveals query counts, cache hits, and template rendering time. I add it only in development settings. The toolbar shows all SQL queries which helps identify N+1 problems. I use the profiler panel to find slow code. The cache panel

I use PageNumberPagination for simple, bookmark-friendly pagination and CursorPagination when data changes frequently (prevents duplicate/missing items between pages). Creating a custom pagination class lets me control page_size, page_size_query_param